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Abstract Seasonal phytoplankton blooms in Greenland’s coastal waters form the base of marine food webs and contribute to oceanic carbon uptake. In Qeqertarsuup Tunua, West Greenland, a secondary summertime bloom follows the Arctic spring bloom, enhancing annual primary productivity. Emerging evidence links this summer bloom to subglacial discharge from Sermeq Kujalleq, the most active glacier on the Greenland Ice Sheet. This discharge drives localized upwelling that may alleviate nutrient limitation in surface waters, yet this mechanism remains poorly quantified. Here, we employ a high-resolution biogeochemical model nested within a global state estimate to assess how discharge-driven upwelling influences primary productivity and carbon fluxes. We find that upwelling increases summer productivity by 15–40% in Qeqertarsuup Tunua, yet annual carbon dioxide uptake rises by only  ~3% due to reduced solubility in plume-upwelled waters. These findings suggest that intensifying ice sheet melt may alter Greenland’s coastal productivity and carbon cycling under future climate scenarios. 

Abstract Numerous proposed geoengineering schemes to mitigate climate change and its consequences are now widely discussed in the scientific literature. Sea level rise is a clear example of the implications of climate change with a further committed rise of at least 2–3 m embedded within the Earth System from +1.5°C of global warming. A bold suggestion to reduce sea level rise is to install underwater barriers to reduce the inflow of oceanic heat around Antarctica and Greenland. Inflow of warm, saline water masses drives ice melt and the destabilization of tidewater glaciers. Whilst the basic theory that barriers would stem oceanic heat flow is uncontroversial, the extent to which barriers might reduce future ice mass loss is less certain. There are numerous concerns about the viability and side‐effects of this proposed intervention. We use existing field observations and representative fjord‐scale models for the Greenland's largest glacier, Sermeq Kujalleq in the Ilulissat Icefjord, to suggest that there is already sufficient evidence to conclude that artificial barrier installation would have negative regional implications for marine productivity. The effects on fisheries are a concern as negative implications for Greenland's regional fisheries are unlikely to be socially acceptable. Increasing “geoengineeringization” of the Earth Sciences is likely to continue in coming decades as society grapples with the challenges of slowing climate change and mitigating its consequences. To produce beneficial results, the technical and social viabilities of geoengineering concepts need to be considered in parallel, with the latter determined in a complex social, economic and cultural nexus. 

Abstract Subglacial discharge emerging from the base of Greenland's marine‐terminating glaciers drives upwelling of nutrient‐rich bottom waters to the euphotic zone, which can fuel nitrate‐limited phytoplankton growth. Here, we use buoyant plume theory to quantify this subglacial discharge‐driven nutrient supply on a pan‐Greenland scale. The modeled nitrate fluxes were concentrated in a few critical systems, with half of the total modeled nitrate flux anomaly occurring at just 14% of marine‐terminating glaciers. Increasing subglacial discharge fluxes results in elevated nitrate fluxes, with the largest flux occurring at Jakobshavn Isbræ in Disko Bay, where subglacial discharge is largest. Subglacial discharge and nitrate flux anomaly also account for significant temporal variability in summer satellite chlorophyll a (Chl) within 50 km of Greenland's coast, particularly in some regions in central west and northwest Greenland. 

This dataset contains time series output from Regional Ocean Modeling System (ROMS) simulations investigating the impact of fjord sill depth on circulation and biogeochemistry in a Greenland fjord system. The data includes three scenarios with different sill depths (250m baseline, 200m, and 100m) and provides fjord-averaged temperature, dissolved inorganic nitrogen (DIN) fluxes at the fjord mouth, cumulative DIN export, and mean DIN concentrations at the fjord outlet. Temperature differences between the baseline and modified sill scenarios are also included. These results demonstrate how fjord sill depth controls water mass exchange, heat transport, and nutrient cycling in glacial fjord systems. Data is provided as a MATLAB structure with metadata describing variables and scenarios.